Cursor is set to move by increments. how to reset to normal?
It sounds like you may have accidentally enabled Transform Snapping (&#8679; Shift&#8633; Tab).

By default transform snapping will snap objects to fixed increments as they are being transformed.


  Transform snapping:
  The ability to snap Objects and Mesh element to various types of scene
  elements during a transformation is available by toggling the magnet
  icon (which will turn red) in the 3D view's header buttons.
  
  Increment:
      Snap to grid points. When in Orthographic view, the snapping increment changes depending on zoom level.


You can disable it by clicking the magnet icon in 3D view > Header, or by pressing Shift+Tab:

Enabled

Disabled
 

For Version 2.8.